Implantable medical devices such as electrical stimulators or fluid delivery pumps, may be used to deliver therapy to patients to alleviate any of a variety of symptoms or conditions. Electrical stimulators, for example, may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. In general, an implantable stimulator may deliver stimulation therapy (e.g., neurostimulation therapy) in the form of electrical pulses or continuous waveforms. An implantable stimulator may deliver stimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patient. Hence, stimulation may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SC S), pelvic stimulation, gastric stimulation, or peripheral nerve stimulation. Stimulation also may be used for muscle stimulation, e.g., functional electrical stimulation (FES), to promote muscle movement or prevent atrophy.
In general, a clinician selects values for a number of stimulation parameters in order to define the electrical stimulation therapy to be delivered by the implantable stimulator. For example, the clinician may select stimulation parameters that define a current or voltage amplitude of electrical pulses delivered by the stimulator, a pulse rate, a pulse width, and a configuration of electrodes that deliver the pulses, e.g., in terms of selected electrodes and associated polarities. The stimulation parameters selected by the clinician may be referred to as a “stimulation program.” In some cases, therapy corresponding to multiple programs may be delivered on an alternating or continuous basis, as a group of programs.